Manafort ties to Russian oligarchs exposed

Paul Manafort, former campaign manager for President Donald Trump, had three US passports, millions in assets and ties to Russian oligarchs, according to federal court documents after his indictment on tax fraud and money laundering charges.

Manafort and associate Rick Gates pose a significant flight risk because of the serious nature of the charges, the strong evidence of guilt, their wealth and "their history of deceptive and misleading conduct," federal prosecutors said in a filing on Tuesday in US District Court for the District of Columbia.

Manafort, 68, and Gates, who also worked on Trump's campaign, pleaded not guilty on Monday in a 12-count indictment, ranging from money laundering to acting as unregistered agents of Ukraine's former pro-Russian government.

The charges came as part of federal special counsel Robert Mueller's five-month-old investigation into alleged Russian efforts to tilt the 2016 presidential election in Trump's favour and potential collusion by campaign aides.

The allegations are not related to campaign activities but reveal close ties to Russia and include activities from 2006 to 2017, which overlaps with the mens' work on Trump's campaign.

The two men are under house arrest and have relinquished their US passports, with a $US10 million ($A13 million) bond set for Manafort and a $US5 million bond for Gates.

"Both defendants have substantial ties abroad, including in Ukraine, where both have spent time and have served as agents of its government," according to the government's memorandum in support of the conditions of release.

"And both Manafort and Gates have connections to Ukrainian and Russian oligarchs, who have provided millions of dollars to Manafort and Gates."